The characteristics of health systems and the environment they operate in affect the effective implementation of patient centered outcome research (PCOR) practices. This, in turn, influences the quality of healthcare patients receive. Yet little is known about the specific characteristics of health systems today that make them more effective at delivering high quality patient care, in part because so much has changed within health care systems due to recent innovations and new models of patient care. The fundamental purpose of the Data Core is to support the work being conducted within the RAND-Penn State Center of Excellence, which is focused on identifying key attributes of health care systems that are likely to be important for successful implementation of PCOR practices and, hence, improved patient outcomes. The data core will accomplish this in two main ways. First, it will focus on collecting, improving, and analyzing primary and secondary data in five regions so as to assist Center investigators with the identification and testing of key characteristics of health systems that may be associated with improved patient outcomes. Second, through this research, the Data Core will develop a novel taxonomy of health systems that can be used to classify health care systems and identify those that are highly effective in implementing PCOR practices. The Data Core also will provide the essential infrastructure for maximizing the efficiency, consistency and quality of the data operations and research conducted throughout the Center of Excellence. This will be accomplished by minimizing unnecessary duplication of effort involved with cleaning data, creating measures, constructing data files, and resolving difficult methodological problems. The Data Core will help to facilitate sharing of information and metrics useful for analyses across the component projects and other investigators in the field.